Oxidation of hydrocarbons



Nov, 6, 192s.

A. w. BURWELL OXIDATION or HYDRQCARBONS Filed sep`t.13. 1922 33T@ mtl @Wmkl um Wm zorro (um Patented Nev. 6, 192s.

ARTHUR WfBUB'WELL, 0E CHAGRIN FALLS, OHIO, ASSIGNOR, BY DIRECT AND MESNE l PATENT OFFICE.

ASSIGNMENTS, TO ALOXOHEMICAL CORPORATION, 0F NEW YORK, N. Y., .A COB- POBATION 0F NEW .YORK

OXIEATION 0F HYDB'JGABBONS.

Application led September 13, 1922. Serial No. 588,075.

This invention relates to a process for the controlled oxidation of hydrocarbons for the production of useful oxidation products, such as, alcohols, aldehydes and acids.

I have found that the hydrocarbon of the aliphatic series, such as are found in petroleum oils or distillates, and aromatic hydrocarbons having an aliphatic side chain attached to the nucleus, such as the hydrocarbons occurring in the products of the destructive distillation of .coal and other organic materials, may be oxidized under properly controlled conditions of temperature and pressure by means of oxygen or air or other oxidizing gas or agent with or without a catalytic agent or-ox gen carrier toproduce economical yields o useful oxidation products.

The invention therefore relates to the processy of oxidizing hydrocarbons generally under controlled conditions which will be described hereinafter in connection with the description of a process of oxidizing petroleum hydrocarbons to form organic acids for which oxidation the process is 1 more particularly designed.

A feature of the invention is the controlled or selective production of either the simple acids, that is, acids containing only the carboxyl group, and the hydroxy acids, that is, acids containing both the carboxyl group and one or more hydroxyl groups.

The accompanying drawing illustrates apparatus suitable for carrying out the process. The apparatus comprises in general a reaction vessel provided with suitable controlled o enings for the introduction of the hydrocar on and the oxidizing agent and for the removal of liquid and gas. The reaction vessel also is provided with means for'indicating the temperature and pressure, a safety vent to relieve excessive ressure, means for heating the contents o ,the reaction. vessel and means for agitating the contents of the reaction -vessel. to secure intimate contact between the hydrocarbon and the oxidizing agent.

Referring to the drawing, 1 is a cylindrical vessel which may be formed of any suitable material capable of withstanding the heat andk pressure employed, preferably an iron ror copper or other metal pipe arranged horizontally. The pipe 1 is provided with end closures or caps 2 and which are Y ber.

`carried on the cap 3. The projecting end of the shaft 5 carries a pulley 7 or other suitable means for rotating the shaft. Mounted on the shaft 5 are a large number of parallel spaced discs of wire screen 8. The discs 8 preferably are positioned close together being spaced by washers 9 as illustrated, and are circular and extend close to but to not touch the walls of the pipe 1. The discs 8 are made of iron, copper or other suitable metal or material and preferably are formed of wire screen although they may be perforated discs or plates of sheet metal or other material. 10 is a filling tube provided with a closure through which hydrocarbon is supplied to the-reaction cham- K 11 isa safety gas outlet which is adjustable for use to maintain a constant maximum pressure in the apparatus. v12 is the oxidizing igas supply inlet pipe and 13 is the draw-o pipe for the liquid product of the reaction. 14 is a thermometer. 15 is a pressure gauge. Suitable means, not illustrated, are provided for heating and cooling the reaction vessel and its contents, for instance, an ordinary oil or'gas burner positioned under the pipe 1 for heat-ing and a water sprinkling pipe above the tube 1 vfor cooling.

The process is carried out as follows:

The cylinder is charged about half full, that is, up to the level of shaft 5 with the hydrocarbon to be oxidized. The hydrocarbon employed will dependnpon the prodnot beso fast as to work the liquid contents of the vessel into a spray or foam. In experimental apparatus in which the tube 1 is about-8 inches in diameter and the discs 8 are made of screen wire of about #6 mesh #18 iron wire, the rate of rotation may vary from 20 to 100 revolutions per minute, preferably about 30 rvolutions a minute. The temperature,I pressure, rate of supplyof oxidizing gas and rate of rotation of the agitator shaft preferably are regulated so that the process is self-sustaining, that is, the reaction continues without the further application of heat, the heat necessary for the reaction being supplied by the reaction itself.

The self-sustaining reacting conditions for any particular hydrocarbon or hydrocarbon mixture, oxidizing gas, size of apparatus etc., are readily determined. Self-sustaining reacting conditions are indicated when the temperature of the reaction vessel remains constant without the application of heating or cooling medium. The rate of reaction can be varied in the following ways: The pressure within the ,reaction Vessel may be increased by adjustment of the gas outlet 11. Increase in pressure increases the rate of reaction. The rate of reaction is increased also by increasing the agitation from the minimum, that is, no agitation up to -the point at which undesirable foam or spray is formed, this condition being indicated by the discharge of liquid hydrocarbon through the gas outlet 11. The rate of reaction is increased also by increase in temperature and within reasonable limits by increase in the rate of supply of oxidizing gas. If the oxidizing gas used is pure oxygen the rate of reaction is nearly directly proportional to the rate of gas supply, but if a1r is used the inert nitrogen gas present exerts a cooling effect and for this reason it may be found that an excessive supply of air will cool the reaction mixture and t retard the reaction.

I have found that the reaction conditions may be practically standardized for a wide range o hydrocarbons since a fairly wide variation in the composition of the hydrocarbon requires only a very small variation in the reaction conditions and in many cases no change in the reaction conditions is required. On a rather wide range of petroleum distillates, among which are mentioned a 32 B spindle oil distillate and a 41 B distillate from Pennsylvania crude oil,

substantially the following reacting conditions have been employed. Rate of rotation of agitator 30 revolutions per minute; temperature 120 C. to 130 C.; pressure 150 pounds per squareinch; air supply at a rate suiicient that the oxygen content of the air is reduced about 40 ercent. Some adjustment of reaction con 'tions of course is ad- Visable. For instance, in treating a more volatile hydrocarbon a higher ressure and a lower rate of air supply shou d be used to minimize Volatilization of the hydrocarbon while in treating a hydrocarbon of high boiling point a lower pressure and a higher rate of air supply may be used. I have found" that the pressure may vary from 100 to 200 pounds per square inch but in general a pressurev of about 180 pounds to the square inch is the maximum pressure at which the process may be carried out Without cooling. At above 180 pounds pressure the temperature tends to rise rapidly.` A pressure of about 100 pounds is re uired to make the process self-sustaining un er other appropriate reaction conditions. As stated, I prefer a pressure of about 150 pounds. If gas more rich in oxygen than air isernployed the temperature, ressure, and rate of agitation, particular y the pressure, should be correspondingly reduced, and if gas less rich in oxygen is employed the temperature, pressure and rate of agitation', particularly the pressure, should be increased.

I have found that by operating with petroleum distillates of -the 'kind mentioned and under the preferred reaction conditions described I am able to form organic acids capable of forming water soluble sodium salts at the rate of about 5 percent per hour calculated on the weight of the batch of oil treated.

For the production of the simple carboxylic acids as the principal product the oxidation should not be carried beyond the point at which the total acid content of the hydrocarbon mixture treated is about 20 percent. When the simple fatty acids are desired the oxidation is carried to this point and the batch is withdrawn from the a paratus and treated with a suitable alka i, for instance, a vwater solution of caustic soda.` The acids dissolve in the water solution which is separated and the oil is re' to acid. A separation of the hydroxy acids from the reaction mixturemay be'accomplished by gravity because the hydroxy ac ids are only sparingly soluble in the sim le acids and t e unchanged oil. A. practica y thev batch o complete separation of the hydroxy acids from the oxidized mixture may be obtained by adding to the oxidized mixture fresh hydrocarbon distillate and separating the hydroxy acids fromthe unoxidized oil and simple acids by gravit In either case, whetlier the hydrocarbon is oxidized to form the simple acids or the hydroxy acids, both types of acids are formed. To recover the two kinds of acids separately the oxidized mixture is iirst subjected to gravity 'separation to recover the hydroxy acids and is then washed with alkali to recover the simple acids and the residual hydrocarbon is returned to the oxidiz` ing apparatus. This procedure of course accomplishes only a crude separation and is effective only when the oxidation is carried to the point at which the hydroxy acids are the principal product. When the hydrocarbon is only oxidized to the extent of about 20 per cent the gravity separation is omitted and the wholeof the acid content recovered by treatment with alkali.v The acidsare then recovered from the alkali by means of acid and the hydroxy acids are separated by treating the mixture with strong sulfuric acid which dissolves the hydroxy acids and at the same time removes colored impurities from the undissolved simple acids.

I have found that in starting the process with new ap aratus it is desirable to add to fp hydrocarbon to be oxidized a catalytic agent or ox gen carrier. The known hydrocarbon-solu le organic salts or compounds of manganese iron and copper havebeen found to be suitable. The addition of such compounds promotes the initial oxidation of the hydrocarbon. After the apparatus has been used for a time the surfaces in contact with the hydrocarbon apparently develo catalytic properties and the use of adde catalytic agents is unnecessary, the reaction rate being substantially the same without the addition of a catal tic agent as when the catalytic agent is use I claim:

1. Process which -comprises agitating a normally liquid hydrocarbon containing analiphatic chain, in liquid phase, in contact with an oxidizing gas at a temperatureof at least about 100o C. and at a` pressure of from about 100 pounds to about 320 pounds per square inch.

2. l rocess which comprises agitating a normally liquid petroleum hydrocarbon in liquid phase in contact with a stream of air at a temperature of from about 120 C. to about 130o C. and at a pressure of about 150-180 pounds per square inch.

3. Process as defined in claim 2, in which the stream of air is supplied to and removed lfrom contact with the hydrocarbon at such a rate that about 40 per cent of its oxygen content is consumed.

4. Process which comprises agitating at a temperature above about 120 C. and at a pressure of about 150480 pounds per square inch a normally liquid petroleum hydrocarbon in liquid phase, in the absence of alkalies, in contact with a stream of air supplied to and removed from contact with the hydrocarbon at such a rateA that about 40 per cent of the oxygen content of the air is consumed, separatin the resultin hydroxy carboxylic acids rom the liqui and subsequently treating the liquid with an aqueous solution of a caustic alkali.

In testimony whereof, I aix my signature.

ARTHUR W. BURWELL. 

